1. Field of the Invention
The present invention relates to a method for manufacturing a microfabrication apparatus, which is specifically preferable for manufacturing Micro Electro Mechanic Systems (hereinafter, it is referred to as MEMS) or a Rugate Filter, these apparatuses are required to process a thin functional material film ranging from several xcexcm to 100 xcexcm or more as a pattern with high aspect ratio ranging from 3 to 10 or more.
2. Description of the Related Art
In MEMS, a microstructure is formed by processing a functional material film such as piezoelectric materials or magnetic materials. For achieving a desired sensing function or actuation function in practical use, the microstructure is required to have at least several xcexcm thick or more, desirably, 100 xcexcm thick or more, and is patterned in a manner of obtaining high aspect ratio.
Among them, the piezoelectric material can be both sensor and actuator functions, so that there are the following advantages: a structure can be simplified in case of using a single function in either one of the above two functions, and the piezoelectric material can be applied to use for the both functions. Therefore, the piezoelectric material is especially expected to use as a component material of a main operation portion of MEMS. Similarly, in a micro fabrication apparatus such as the rugate filter using optical functional materials, for instance, a technique where a thick functional material is processed as a pattern with high aspect ratio, is earnestly required besides MEMS.
In case of employing the piezoelectric material for a microactuator such as micropump, a small-sized ultra sonic motor, and a micro cantilever, or for a micro ultra sonic source, practical performance distance or output is required. Hence, take PZT, which is a solid solution of lead titanate and lead zirconate (Pb (Ti, Zr)O3; hereinafter it is referred to as PZT) for instance, a thick layer of at least about several xcexcm is needed, further desirably, a thick layer ranging from several 10 xcexcm to 100 xcexcm or more is useful.
Conventionally, the structure of the functional material film made of the above piezoelectric material is manufactured by a mechanical processing performed in bulk materials or a screen printing method. For this reason, the mechanical processing and the screen printing method are techniques capable of forming a pattern in a thick film. As other methods, for example, a technique where thin films are laminated many times with sputtering or a CVD (Chemical Vapor Deposition) method, is suggested.
However, in the mechanical processing, the functional material film is hard to be patterned accurately because failure of members occurs during processing or handling, or characteristics vary when adhering.
In case of the screen printing method, sintering temperature rises at 500 to 800xc2x0 C. or more, so that the substrate and other structure members tend to be damaged, and additionally, the film is hard to be formed in high density. With the above reasons, there is a tendency where optimum quality as a functional material layer is failed to obtain.
Further, in the technique where a thick film is formed with sputtering or the CVD method, a process of forming film at comparatively low temperature can be generally conducted. Meanwhile, deposition of the thick film of several 10 xcexcm or more considerably takes time, so that the above technique is not suitable for manufacturing process in practical use. Additionally, there is a tendency that accurate etching process is difficult to be performed in the functional material film formed by depositing many times for a long time.
A thick film made of the functional material may be formed with the sputtering or the CVD method, then is patterned with a lift-off method in stead of etching. Here, in general, the lift-off method is a method such that photoresist is used as a pattern, then the pattern is separated in order to gain a desired pattern.
However, with the lift-off method, only a functional material film formed at low temperature can be formed. For this reason, in case of using photoresist as a pattern, deformation or burning occurs in photoresist when heating the substrate at about 150xc2x0 C. or more. This fails to perform the lift-off method, hence, a method for forming the functional material film is strictly limited due to processing temperature.
According to a LIGA (Lithographie Galvanoformung Abfprumng) process employing a X-ray lithography, resist can be realized to pattern in several 100 xcexcm. However, this method is not industrially practical in the following points: a X-ray lithography apparatus is unusual and expensive; special structure using a material having sufficient shielding characteristics (e.g. Au (gold) ) for a X-ray having high permeability is employed, and an expensive complicated photomask is needed for manufacturing.
As other lift-off methods, it is suggested that a SiNx film or SiO2 film is employed. In this case, forming layer can be performed at high temperature, so that limitation on the processing temperature eases. On the other hand, the SiNx film or the SiO2 film is extremely difficult to be patterned in the aspect ratio 3 or more.
As described above, each of the conventional techniques has the problems such that the thick film made of the functional material having at least several xcexcm or more is difficult or impossible to be patterned in the high aspect ratio 3 or more. As a result, various microfabrication apparatuses excellent in performance characteristics can not be realized.
The invention has been achieved in consideration of the above problems and its object is to provide a method for manufacturing a simple and practical microfabrication apparatus achieving MEMS and the rugate filter excellent in performance characteristics by patterning a thick film made of a functional material film.
A method for manufacturing a microfabrication apparatus comprises steps of forming a mask pattern by providing a trench or a gap deeper than a desired functional material layer within a semiconductor layer, depositing the functional material layer in a manner to be thinner than the semiconductor layer, and obtaining a pattern of the functional material layer by removing the mask pattern.
A method for manufacturing a microfabrication apparatus comprises steps of forming a mask pattern by coating a surface of a photoresist layer with a cap film after a trench or a gap deeper than a desired functional material layer is provided within the photoresist layer, depositing the functional material layer in a manner to be thinner than the photoresist layer at least in the trench or the gap of the mask pattern, and obtaining a pattern made of the functional material layer by removing the mask pattern.
A method for manufacturing a microfabrication apparatus comprises steps of forming a mask pattern by providing a trench or a gap deeper than a desired functional material layer within an organic compound film, depositing the functional material layer in a manner to be thinner than the organic compound film at least in the trench or the gap of the mask pattern, and obtaining a pattern of the functional material layer by removing the mask pattern.
According to the method for manufacturing the microfabrication apparatus of the present invention, a semiconductor layer is employed as a mask pattern in order to form a trench or a gap deeper than a desired functional material layer, and the functional material layer (film) is formed on the whole surface including a bottom of a concave part of the trench or the gap. The advantages of the semiconductor layer are withstood a process for forming the functional material layer conducted at high temperature, patterned in high aspect ratio, and achieves excellent process consistency for the whole manufacturing processes of the microfabrication apparatus. The functional material layer deposited on the mask pattern is removed with the mask pattern itself. Then, the functional material layer deposited on the bottom of the concave part of the mask pattern only remains selectively in order to obtain a desired pattern of the functional material layer. In this time, the trench or the gap deeper than the functional material layer is provided in the mask pattern, so that the functional material layer is disposed on the mask pattern and in the bottom of the concave part of the mask pattern in a manner to be separated between a pattern edge of the functional material layer disposed on the concave part of the mask pattern and a pattern edge of the functional material layer disposed on the mask pattern. Accordingly, the mask pattern is removed (lift-off) performed while both sides of the pattern edges of the functional material layer disposed on the concave part of the mask pattern keeps intact.
In the method for manufacturing another microfabrication apparatus according to the present invention, instead of using the semiconductor layer as a mask pattern, a photoresist layer further excellent in process consistency is patterned and coated its surface with a film cap, and employed.
In the method for manufacturing another microfabrication apparatus according to the present invention, instead of using the semiconductor as a mask pattern, an organic compound film is employed. The organic compound film is adapted to a larger pattern and can be patterned or separated more simply.
A silicon substrate, which can be processed simply is employed as a semiconductor layer, and the silicon substrate may be bonded on another substrate such as a grass substrate with an anodic oxidation method, which is a simple process. A silicon portion of a SOI (Silicon On Insulator) substrate, which can be obtained with a simple process may be employed as a semiconductor layer.
Other and further objects, features and advantage of the invention will appear more fully from the following description.